Breaking the silence about Spring

Did you know that in 1965 the U.S. Department of Agriculture planted a particular variety of lilac in more than seventy locations around the U.S. Northeast, to detect the onset of spring — in turn to be used to determine the appropriate timing of corn planting and the like? The records the USDA have kept show that those same lilacs are blooming as much as two weeks earlier than they did in 1965. April has, in a very real sense, become May. This is one of the interesting facts that you’ll read about in Amy Seidl’s book, Early Spring, a hot-off-the-press essay about the impacts of climate change on the world immediately around us – the forest, the birds, the butterflies in our backyards.

The brilliant title of Seidl’s book was one of the reasons that it caught my attention. The other was that I have realized I need to better educate myself about the impact of climate change on everyday life. I’ve been dismissive of the idea that the average person can really detect the impacts of recent warming on, for example, the timing of the apple-blossom season, but I’ve been taken to task by several of RealClimate’s readers for this. If you are paying attention, they have argued, the changes are actually rather obvious.

Of course, Amy Seidl is not the average person. Rather, she’s a trained ecologist with a Ph.D. (as well as an avid gardener) and she’s clearly paying extremely close attention. Her book is the first one I have read that effectively brings home the tangible impacts that global warming will have – is having – on our everyday lives. “We are increasingly familiar,” she writes, of images of melting glaciers, “but how do we give them relevance in our lives? From my window I see no glaciers.” She answers her own question with a series of vignettes, some from her own experiences, many more from her extensive research (well referenced throughout the book).

Cardinals, robins and cowbirds are all arriving earlier in Vermont than they did a century ago. Kingfishes, fox sparrows and towhees are not. Why the difference? The answer, as Seidl explains, is that the former group has the ability to respond ecologically to the changes, because these birds cue their arrival to temperature. The latter, it appears, respond more directly to temporal cues, that won’t change even as climate does. It’s obvious from this example that the make up of bird life in Vermont – the species distribution – will change over time. This may not necessarily be a bad thing of course. On the other hand, it turns out that the robins are the most important host for West Nile virus; the early bird gets the worm, so to speak, and passes it along to humans.

Maple seedlings need about 100 days of below-freezing weather. As this becomes rarer, fewer maples will populate the forests. This, Seidl explains, is why species-range models predict the decline and eventual loss of sugar maple (at least in New England) in the future. But, she notes, the models don’t take into account the full complexity of the system, such as the impact of competition among different species. So we don’t really know what will happen, or how fast. What we do know is that maple-sugar farmers have noticed – and documented – an earlier maple sugaring season over the last few decades.

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